Go-ahead for ESA's new millennium space observatories Planck and FIRST

European scientific institutes has been given the go-ahead for the
development of instruments for two major ESA missions for the new
millennium: Planck, a satellite to study the radiation considered to be
the "echo" of the Big Bang and FIRST, an infrared space telescope. ESA's
Science Programme Committee (SPC) approved on 17 February the scientific
instruments for both missions, which will be built by more than 80
institutes from all around Europe. The go-ahead will also allow ESA and
European industry to begin in earnest the development of the Planck and
FIRST spacecrafts.

Planck and FIRST will be launched together in the year 2007.

Planck is a cosmology mission, designed to test the models describing
the origin and evolution of the early Universe. It will do so by
studying the Cosmic Background Radiation, a light emitted shortly after
the Big Bang that fills the whole Universe and can be detected today,
like an "echo" of that primeval explosion. Astronomers consider it a
"fossil" radiation, since it holds a lot of information about both the
past and the future of the Universe.

"Planck will determine fundamental characteristics of the Universe, such
as its geometry, its density, and the rate at which it expands. It will
also provide important clues as to the kind of matter that fills the
Universe", explains Planck Project Scientist Jan Tauber, at ESA's
European Space Research and Technology Centre (ESTEC) in The
Netherlands.

More precisely, the task of Planck will be to measure the temperature of
the "echo" of the Big Bang over the whole sky. Though at the time of its
emission the Cosmic Background Radiation was very hot, some 3000
degrees, it has since expanded and cooled together with the entire
cosmos to a much lower temperature, namely about minus 270 degrees
centigrade (3 degrees Kelvin).

Planck will look for differences in this temperature as slight as a few
microkelvin, thin variations like clots that are, in fact, the "seeds"
of the huge condensations of matter in today's Universe. "It will be
like watching the birth of the galaxies, the galaxy clusters, all the
large-scale structures that we observe today", Tauber says.

The two instruments on board Planck, now approved by ESA, are the Low
Frequency Instrument (LFI) and the High Frequency Instrument (HFI).They
will cover a very broad range of frequencies (between 30 and 857
Gigahertz).

The HFI will be designed and built by a Consortium of about 20
institutes led by Jean-Loup Puget of the Institut d'Astrophysique
Spatiale in Orsay (France). The LFI will be designed and built by a
Consortium of about 20 institutes led by Reno Mandolesi of the Istituto
di Tecnologie e Studio delle Radiazioni Extraterrestri in Bologna
(Italy).

FIRST, the "Far InfraRed and Submillimetre Telescope", is the successor
of ESA's Infrared Space Observatory ISO. It will be more powerful than
any of its predecessors, with a primary mirror of 3.5 metres in diameter
- the largest ever for an infrared space telescope. It will observe at
wavelength's range never covered before (from 80 to 670 microns). Like
Planck, it will be located about 1.5 million kilometres away from
Earth.

FIRST will look for planetary systems and study processes like the
evolution of galaxies in the early universe. It will provide very
detailed information about the coldest objects in the Universe, and
those enshrouded by dust. The pre-stellar cores from which the stars
hatch at nearly minus 260 degrees C, or the dusty distant galaxies
undergoing violent collisions are some examples. Also, FIRST will show
the composition, temperature, density and motion of the gas and dust of
the clouds in the interstellar space.

Its payload will consist of three instruments: two cameras called PACS
and SPIRE, and HIFI, a high-resolution spectrometer. "They are real
technological challenges. Instruments like these have never been used in
a space telescope", says FIRST Project Scientist Goeran Pilbratt, at
ESA/ESTEC.

To avoid the "noise" caused by the emission of the instruments
themselves, a cryostat full of superfluid liquid helium will cool them
down to a temperature below minus 271 degrees C, very close to the
absolute zero (at -273 degrees C).

The Heterodyne Instrument for FIRST (HIFI) takes very high resolution
spectra of the astronomical objects in thousands of frequencies
simultaneously. It will be designed and built by a consortium led by
Thijs de Graauw, SRON, Groningen, in The Netherlands.

The Photoconductor Array Camera and Spectrometer (PACS) instrument is an
infrared camera and a spectrometer that will be developed and built by a
consortium led by Albrecht Poglitsch, MPE, Garching, in Germany.

The Spectral and Photometric Imaging REceiver (SPIRE) is also a camera
and spectrometer, but will observe at longer wavelengths than PACS. It
will be developed and built by a consortium led by Matt J. Griffin,
Queen Mary and Westfield College, London, UK.

ROYAL ASTRONOMICAL SOCIETY PRESS NOTICE

27th March 1998

NEW SPACE MISSION WILL LOOK BACK TO THE BIG BANG

About seven years from now, an ambitious new space science
mission will get under way with the launch of the European
Space Agency's Planck satellite. Planck will be looking back to a
time shortly after the Big Bang created the Universe. Dr Alan
Heavens of the University of Edinburgh will be describing this
exciting project and the UK's participation during the UK
National Astronomy Meeting at the University of St Andrews.
Dr Heavens is a Scientific Associate for the Planck mission.

The Cosmic Microwave Background

A few minutes after its creation, the Universe had a temperature
of billions of degrees. Since then, it has gradually cooled to the
point where its temperature is now just a few degrees above
absolute zero (-273 degrees C). Since this faint glow was first
discovered in 1965 as the so-called Microwave Background
Radiation, it has played a crucial role in our understanding of
the Universe. The very existence of this radiation is firm
evidence for the Big Bang theory of the expanding Universe.

Since then, the Cosmic Background Explorer (COBE) satellite has
discovered 'ripples' in the temperature of the Universe. These
represent small variations in the density of the material in the
early Universe, and help to explain how matter clumped
together to form stars and galaxies.

Planck

This European Space Agency (ESA) mission, currently scheduled
to fly in about 2005, is a major follow-up to the COBE mission. By
using detectors cooled to within a tenth of a degree of absolute
zero, Planck will map the entire microwave background sky with
unprecedented detail. Its two instruments will operate
simultaneously at nine frequencies, with a sensitivity of two
parts in a million, and an angular resolution of a few arcminutes
(compared with COBE's 7 degree-wide view).

Planck's design gives it the capability of measuring many of the
characteristics of the Universe - its geometry, its contents and its
ultimate fate - to a high degree of accuracy for the first time. By
using Planck to look at the fine detail in the temperature pattern
of the sky, cosmologists should be able to test models for the
origin and structure of the Universe. For example, how fast the
Universe is expanding; whether it will eventually halt its
expansion; the nature and quantity of dark matter, which
appears to be the dominant constituent in the Universe; and the
nature of the initial irregularities - did structure develop from
small quantum fluctuations, or from a more exotic origin?

"It is tremendously exciting that this experiment should answer
not just one, but practically all of the major questions of
cosmology in one go," said Alan Heavens. In addition to this
primary aim, the decoding of Planck's microwave sky maps will
also produce a catalogue of more than 10,000 clusters of galaxies,
and tens of thousands of quasars, starburst galaxies and other
unusual objects. The clusters will be detected by the effect their
hot gas has on the microwave radiation as it passes through
them.

The UK and Planck

The UK's involvement is both in hardware and in the
formidable data analysis task. The following centres are involved
in the High Frequency Instrument:

Queen Mary and Westfield College, London will design and
manufacture filters and some of the optics.

Rutherford Appleton Laboratory and the Royal Observatory
Edinburgh will be involved with the cooling systems.

The University of Leicester will offer electronic ground
support.

The UK data analysis will be centred at the University of
Cambridge and Imperial College, London, and also involve
scientists at Edinburgh.

Nuffield Radio Astronomy Laboratories at Jodrell Bank
(University of Manchester) are designing and building the most
sensitive radio amplifiers ever constructed for the Low
Frequency Instrument.

Planck was formerly known as COBRAS/SAMBA. It is a
medium size mission in ESA's Horizon 2000 space science
programme. ESA is currently examining the possibility of
reducing costs by launching Planck and FIRST (Far Infrared
Space Telescope) on the same satellite.